LAMELLAS TO INCREASE THE MIXED LIQUER SUSPENDED SOLID (MLSS) FOR BIOLOGICAL WASTEWATER PURIFICATION

The European water protection legislation requires the advanced nutrient removal down to 13 mg/l Ninorg. As a result, many sewage treatment plants have to upgrade their biological treatment step. There are two main possibilities to increase the capacity. One is to increase the treatment tankage, the other one is to increase the MLSS in the existing treatment tankage. The problem with increasing the biomass in the existing treatment tankage is the limitation of conventional final clarifiers' separation capacity. The installation of Lamella plate packets in the discharge of the biological reactor provides a pre-sedimentation, recirculates a certain amount of sludge directly back to the reactor, and limits the sludge feed to the final clarifiers.The German Federal Foundation for the Environment supported the investigation to achieve layout criteria and to find out the limits of the lamella assemblies in a rectangular basin. The results show that with this technology, a pre-sedimentation of 1 – 1.5 g/l can be achieved. This means an ss removal efficiency with respect to the biomass concentration in the aeration basin of 25 – 30%.